Modern fence building methods employ large numbers of steel posts in combination with relatively few wooden posts. In some instances steel posts are used exclusively except for corners and/or at gates. However, devices and methods of which applicant is aware for driving steel posts in connection with fence building and other projects leave much to be desired. One method involves standing on the tailgate of a pick-up truck or the like and using a sledge hammer to drive the steel post. This procedure is somewhat dangerous, and the posts are rarely ever driven on the vertical. Another method involves using a tubular piece of pipe closed at its upper end by a weight, positioning the pipe over the top portion of the post, and then reciprocating the pipe by hand to hammer the post into the ground. Some hammers of this type have oppositely disposed handles to allow two persons to operate them. These methods clearly involve a lot of hard work, are slow to implement, and typically result in having a line of steel posts that are not driven vertically into the ground so that the fence has an unsightly appearance unless the posts are bent at the ground to achieve vertical, which can result in weakening the post at the bend.
Various apparatuses have been proposed that briefly store and then release mechanical energy in connection with percussion tools, punches and presses, rock drilling machines, compressors and high pressure pumps. For example U.S. Pat. No. 4,732,220 shows such a device in the form of a hole-punch where a hand crank-operated cam wheel is used to raise and then suddenly release a compression spring-loaded shaft. However, this patent is essentially unrelated to solutions to the problems involved in driving a steel post with a tractor-mounted machine. Indeed, if the patented device were to be mounted on the outer ends of the pivoted draft arms of a tractor, a steel post could not be successfully driven thereby because there is no means to maintain the device in alignment with the post.
A general object of the present invention is to provide a new and improved tractor-mounted steel post driving machine that obviates the above-mentioned difficulties.
Another object of the present invention is to provide a new and improved farm tractor-mounted steel post driving machine having a mast that is automatically aligned with the post throughout the driving operation so that the post can be driven on true vertical.
Still another object of the present invention is to provide a new and improved steel post driving machine of the type described where the mast that carries a reciprocating hammer is maintained in alignment with the post by the post itself as the outer ends of the draft arms on which the mast is mounted are pivoted downward through an arc during the driving operation.